Merchant + Mobile Shop / Web Shop: on-the-fly modification of an ongoing order

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This feature is a continuation of feature #54

This feature allows the customer to change an ongoing order upon Merchant request.

This feature is especially useful if the restaurant runs out on an ingredient (i.e.: pepperoni). It allows the customer to edit on-the-fly the specific product which had the ingredient (pizza) and being able to eliminate it from the order, modify it (select another product variant), or cancel the full order.

When the restaurant is processing the order and realizes a product must be changed it select either the product o the product variant that is unavailable and it notifies the customer of such unavailability. No options, in this case, are suggested.

The customer receives a dialog where he/she has to select between:
- cancel the full order
- drop the product
- modify the product variant for another variant

After the customer's choice the order follows its flow.